x HORNLESS EXTINCT FORMS 259 name denotes/ had also canines and, in one species, six incisors in the lower jaw. This ^Lceratheri'itm had, moreover, four toes in the fore-feet. In the Miocene and later the Hhinoceros existed in Europe and America. There was even a purely northern form, the It"k. ticfaorJiinus, which possessed a woolly covering and had the same range as the Mammoth. This Rhinoceros was two- horned. The post-Pliocene and European ElasmotJierium was a colossal rhinocerotine creature. This great beast had two horns and a body 15 feet long. Its limbs are not known, and as the teeth are different from those of Rhinoceroses in general, it may not have belonged to this group at all, though Osborn is inclined to derive it from A.ceratlieriutti3 admitting at the same time that the evidence is " decidedly slender." The teeth in fact are like those of a Horse in being bypselodont and prismatic in form. As to the two horns, they were apparently not exactly like those of typical Rhinoceroses; there was an enormous horn posteriorly, supported on a huge boss of bone, and in front of this a roughened spot suggests a smaller or at least a much more slender horn. It is important to notice that fossil Hhinoceroses belonging to the restricted genus ^Rhinoceros were in Europe invariably two- horned ; it is only in India, where they still exist, that one-horned forms are met with in a fossil state. The [Rhinoceroses of America were mostly hornless. Dicera- therium is an exception ; but in many cases it had two parallel not successive horns, and these were, to judge from the slight promi- nences, but feeble in development, and perhaps hardly exactly comparable with the formidable weapons of the Old-World forms. ^Lceratheriu'm tridcwtylum, with indications of paired horns, may be ancestral to Diceratherium. The American forms have weak and slender nasals in correspondence with the absence of horns; the sagittal crest is retained in contradistinction to the great flattened surface of the skull in the horned Rhinoceroses. A.ceratherium of both divisions of the globe probably represents the ancestral group of the horned and the hornless forms. This being the case it is highly interesting to note a distinct convergence in the quite 1 Quite recently, however, a species, A. in&isivum, preserved at Darmstadt, lias been found by Professor Osborn to possess- a slight rugosity upon, the frontal bones, which probably indicates the presence of a rudimentary horn, and tke same author is apparently inclined to place in Aes&ra^i^irium, the homed (see p. 261).